------------[ cut here ]------------
WARNING: CPU: 0 PID: 3341 at net/ipv4/af_inet.c:167 inet_sock_destruct+0x5f6/0x7b0 net/ipv4/af_inet.c:167
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 3341 Comm: syzkaller097296 Not tainted 4.9.77-ge12a9c4 #18
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db207cb8 ffffffff81d941c9 ffffffff83a47bc0 ffff8801db207d90
 ffffffff83f2f000 ffffffff832ebc36 0000000000000009 ffff8801db207d80
 ffffffff8142f3c1 0000000041b58ab3 ffffffff8418ab70 ffffffff8142f205
Call Trace:
 <IRQ> [   28.713936]  [<ffffffff81d941c9>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [   28.713936]  [<ffffffff81d941c9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8142f3c1>] panic+0x1bc/0x3a8 kernel/panic.c:179
 [<ffffffff81131144>] __warn+0x1c4/0x1e0 kernel/panic.c:542
 [<ffffffff811313ac>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff832ebc36>] inet_sock_destruct+0x5f6/0x7b0 net/ipv4/af_inet.c:167
 [<ffffffff835849d2>] l2tp_tunnel_destruct+0x352/0x5a0 net/l2tp/l2tp_core.c:1329
 [<ffffffff82ee5033>] __sk_destruct+0x53/0x570 net/core/sock.c:1428
 [<ffffffff812930f8>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff812930f8>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff812930f8>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff812930f8>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff812930f8>] rcu_process_callbacks+0x898/0x1300 kernel/rcu/tree.c:3037
 [<ffffffff838b9846>] __do_softirq+0x206/0x951 kernel/softirq.c:284
 [<ffffffff81146bc5>] invoke_softirq kernel/softirq.c:364 [inline]
 [<ffffffff81146bc5>] irq_exit+0x165/0x190 kernel/softirq.c:405
 [<ffffffff838b845b>] exiting_irq arch/x86/include/asm/apic.h:659 [inline]
 [<ffffffff838b845b>] smp_apic_timer_interrupt+0x7b/0xa0 arch/x86/kernel/apic/apic.c:960
 [<ffffffff838b46e0>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:741
 <EOI> [   28.787913]  [<ffffffff8113cd84>] ? stack_not_used include/linux/sched.h:3387 [inline]
 <EOI> [   28.787913]  [<ffffffff8113cd84>] ? check_stack_usage kernel/exit.c:713 [inline]
 <EOI> [   28.787913]  [<ffffffff8113cd84>] ? do_exit+0x1324/0x2a40 kernel/exit.c:884
 [<ffffffff81142958>] do_group_exit+0x108/0x320 kernel/exit.c:937
 [<ffffffff81142b8d>] SYSC_exit_group kernel/exit.c:948 [inline]
 [<ffffffff81142b8d>] SyS_exit_group+0x1d/0x20 kernel/exit.c:946
 [<ffffffff838b2c2e>] entry_SYSCALL_64_fastpath+0x29/0xe8
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..